Fix Linux reading of older files

Notice that we do this in reading calchart 3.3 sheets (with the older parser):

```
            auto c = Coord(reader.Get<uint16_t>(), reader.Get<uint16_t>());
```

There's no guarantee of the execution order of reading the two values here.  Should be:

```
            auto x = reader.Get<uint16_t>();
            auto y = reader.Get<uint16_t>();
            auto c = Coord(x, y);
```
